CAREFUL: An NYPD Bomb Squad member examines a gasoline canister left in a vehicle last night. Photo: AP

A couple of 5-gallon gas cans in the back seat of a car parked in Union Square last night brought the area to a screeching halt, prompting the evacuation of 600 people and briefly trapping hundreds of punk-rock fans attending a concert at Irving Plaza.

But it turned out the suspicious car was owned by a gardener who uses gas cans to fill his lawn mower.

The call first came in to cops at 10:16 p.m. from a Con Ed worker on his break who noticed the containers in the car parked in front of the building at 4 Irving Place.

Within moments, cops and Bomb Squad experts swarmed the area to check out the 1991 Oldsmobile.

The cops kept hundreds of fans inside Irving Plaza — where a Buzzcocks concert was about to let out — before finally letting them out the back door.

“So . . . bomb scare,” Tweeted the Dollyrots, the opening band for the punk-rock vets. “We might have to play after the Buzzcocks to keep people here.”

Residents of apartment buildings and NYU dorms and late-night workers were all sent into the street.

By midnight, the owner of the vehicle, who had been at the concert, returned and was none too happy — especially when he saw that cops had blown out his windows with two controlled blasts.